<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css">
</head>

<body>

    <form action="">
        <div class="form-group col-lg-3 form-horizontal">
            <div class="col-lg-7">
                <input type="text" id="idCard" class="form-control" aria-label="身份证号">
            </div>
        </div>
        <div class="dropdown">
            <button type="button" class="btn dropdown-toggle" id="dropdownMenu1" data-toggle="dropdown">
                选择您的职位
                <!-- 3.3.7版的能显示下拉三角 -->
                <span class="caret"></span>
            </button>
        </div>
    </form>

</body>

</html>